Process for the high concentration of impure sulphuric acid treated preliminarily in a dephlegmator



Mamh'lfi, 1931. gusc g g 1,795,995

PRQCESS FOR THE HIGH CONCENTRATION OF IMPURE SULPHURIC ACIFD TREATED PRELIMINARILY IN A DEPHLEGMATOR vim/elder lA/j'jjl 242's alz n/ Filed April 5. 1929 Patented Mar. 10,- 1931 A UN TED [S ATES PATENT-. oFFIceQ WILLI euscniNe, or HALLE, GERMANY rnocnss non THE HIGH CONCENTRATION ermin sutrnunrc ACID TREATED PRELIMINARILY IN Application filed April 5, 1929, Serial No.

There is already known vessels intended and designed for concentration and provided with a pipe or pipes through which the liquid concerned is conducted down to the bottom.

of the respective vessel. A concentration vessel provided with a thus arranged pipe is employed also in connection with the present invention, but in contradistinctionv to what is known there is used in the present case no open basin but closed vessel, or, more precisely, a cast-iron closed vessel, in which the sulphuric acid to be concentrated is-heated to the boiling point, as is known per se. also in connection with known plants for the high concentration of sulphuric acid, for instance in the plantsof the Pauling? type. With these plants the sulphuric acid vapor is conducted into a rectification column in order to be used there as separating agent. The sulphuric acid rectified in the column is continually conducted to the surface of the contents of the respective receptacle, and as the acid supplied thereinto' becomes weaker and weaker by reason of the rectification pro-l cedure in'relation to the vapor rising from the sulphuric acid boiler there. form layers in this boiler, and the detrimental effect thereof is that those portions of the boiler where the acid isin contact with the vapor space are destroyed by corrosion arising just at those portions. In order to obviate this detrimental effect Pauling has provided at the place in question a cast-iron ring. At any I rate, the chief disadvantages are not done away with by that expediency. as the weaker concentrated acid floats upon the surface of the boiler contentsandflows into the cooler,

I whereas the strongly'concentrated acid forms layers in the lower part of the boiler and gives rise to'retardation of ebullition and to superheating of the boiler wall.

The chief dra back of carrying out the concentration in cast-iron boilers is, however, that the impurities present in the recti- 46' tying acid, such as metal salts, organic imthat no superheatingi'in the sulphuric acid A DEPHLEGMATOR.

352,730, and in Germany J'une17, 1927,

purities, and the like, deposit upon the bottom of the boiler and cause a more or less quicklyburning through thereof according to their type and their amount. Besides, the impurities are bad conductors of heat, where- 50 by an increased supply of heat is necessitated in order to concentrate the-acid. The boiler walls are not sufliciently-cooled and there arises,-in consequence thereof, superheating by which the boiler is destroyed in the course of time. I V Moreover, when the concentration is carried out in. that manner in cast-iron boilers, the bottom thereof is subjected to the greatest heatand the generation of vapor is,therefore, strongest just at the bottom, but as the level of the acid ispretty much remote from the bottom the bubblescan rise only with difficulty, that is to i say, can overcome only with difficulty the resistance presented by the verical. height of the acid. in; the boiler. That gives rise to retardation of ebullition and the acid leaves the boiler in the form of The drawbacks and. d'sadvantages dis- I closed inthe 'preceding paragraphs are 'ob-'' vi'ated, accor ding to the present invention, by the featurethatthe :acid Ito'be conce'n f trate d and introduced into th'efllowermost portion o'faclosed cast-iron boiler is stirred i so that a uniform supply of'heat is madeiposs sible. Besides this, the certainty is attained boilercan occur so that vthe'thic'knes'sv of the boiler wall can considerably less than heretofore. Furthermore,'the foreign substances, such: asfnietal salts, iron mud, and the like, $5 present in the boiler are separated bythe stirring so that'the boiler is thereby -auto-- r inatically cleaned; It is also andparticula'r I ly rendered possible to concentrate, the procedure stated, impure sulphuric 391d in a 7 manner perfectly free from disturbances. to now the concentration of this acid has met with extraordinarily great difiiculties owing to the separation and precipitation of the metal salts whereby grave disturbances were caused not only with'PauL ings process, but also with the likewise known process of Kessler.

The greatest advantage, however, which the present improved process presents over the known processes consists therein that one succeeds in producing in continuous service sulphuric acid of from 98 to 98.5% without any loss worth mentioning. This has up to now been impossible since in attempting to manufacture sulphuric acid of 98% the equilibrium is very easily disturbed according to the formula I-Izsoi ssOs +H;O

is introduced into the stirred acid near the bottom of the boiler the contact between the two substancesis by far more intimate than otherwise andthe oxidation agent is utilized in a very high measure which appears from the fact that considerably less air, etc., than otherwise is required.

The improved process is carried out preferably in a boiler designed as shown diagrammatically and by way of example on the ac companying drawing which shows a vertical axial section through the boiler. The acid to be concentrated is introduced into the boiler through the pipe 'a' which is closed at its lower, i. e. inner end but is there proimpure sulphuric acid treated preliminarily P in a dephlegmator or the like, consisting in introducing the impure acid into the lowermost part of a closed vessel, and stirring the acid therein and introducing air into the acid to act at the same time as an oxidizing agent.

In testimony whereof I affix my signature.

VVILLI BUSCHING.

, ice

vided' with a plurality of openings 0. d de'-' notes a stirring member on a shaft 2) which is rotated byany suitable means (not shown);

e is a tube through which the compressed air or anequivalent'agentis introduced into the acid. Instead of providing this separate tube, the shaft of the stirring member (Z may be hollow, and outlet apertures for the air, etc., intro'duced through the hollow shaft may be provided near the lower end thereof.

The arising vapor escapes through the branch 'f, whereas the highly concentrated acid, together with the stirred-up mu-d, the metal salts, and the like through the aperture 9.

these details allow of a member of modifica is withdrawn I 'wi h it,however, to be understood that 

